function ajax_example_add_more

This example shows a button to "add more" - add another textfield, and
the corresponding "remove" button.

It works equivalently with javascript or not, and does the same basic steps
either way.

The basic idea is that we build the form based on the setting of
$form_state['num_names']. The custom submit functions for the "add-one"
and "remove-one" buttons increment and decrement $form_state['num_names']
and then force a rebuild of the form.

The $no_js_use argument is simply for demonstration: When set, it prevents
'#ajax' from being set, thus making the example behave as if javascript
were disabled in the browser.